There are numerous trigger mechanisms capable of being locked in safe, semi-automatic, burst, and fully automatic operation. Different variations of rifles will allow some or all of the various modes of operation. Selector mechanisms have been developed for use with the trigger mechanisms to select between some or all of the various modes.
In firearms limited to safe and semi-automatic modes of operation, one of the drawbacks to the trigger mechanism occurs when the hammer is returned to the cocked position by the bolt carrier. After firing a round, the bolt carrier moves rearwardly, contacting the hammer and pivoting the hammer backwards into the cocked position. This action results in the sear hook at the striking end of the hammer directly striking the hammer-receiving surface of the disconnector and transferring energy to an operator's finger upon the trigger in the form of a sharp snap or forward movement of the trigger. After repeated firings of the weapon, this trigger snap can begin to cause bruising or other injury to the finger, making continued firing uncomfortable.
Another drawback to the trigger mechanism occurs after firing when the trigger nose resets into the trigger notch of the hammer to prevent forward motion of the hammer preparatory to firing by another trigger pull, where there is a substantial pause as the hammer travels rearwardly from the cocked position, to the past-cocked position, and then forwardly to the cocked position preparatory to firing by another trigger pull. This pause inherently limits the speed of repeated trigger pulls in the semi-automatic mode of operation, which, for many competitive shooters, is not satisfactory.
A further drawback to the trigger mechanism occurs during the pull of the trigger to initiate the firing of a round. In conventional trigger mechanisms, the pull of the trigger occurs in one, uncontrolled stroke. The trigger snap that inherently occurs during the trigger pull can compromise aim and lead to missed shots, especially when shooting at targets that at long distances downrange.
Accordingly, there is a need in the art for trigger mechanisms that limit trigger snap and that improves the trigger-to-hammer reset between trigger pulls in the semi-automatic mode of operation, and that provides a staged trigger pull for providing a controlled trigger pull for improving accuracy downrange.